WASHINGTON -- A top U.S. official for the Middle East says the "tipping point" in Syria must come "quickly."

Jeffrey Feltman, the assistant secretary of state for Near Eastern affairs, said during testimony before the Senate Foreign Affairs Committee, "We don't know for sure when the tipping point -- the breaking point -- will come in Syria, but it will come."

He also said the end President Bashar al-Assad's rule must come "quickly," as "the longer the regime assaults the Syrian people, the greater the chances of all-out war and a failed state."

Testifying alongside Feltman, U.S. Ambassador to Syria Robert Ford said that "the Assad regime is under greater stress now, I think, than it was even two or three months ago" due to sanctions and military desertions.

The United Nations says over 7,500 people have been killed since the crackdown on antigovernment protests began one year ago.